(1) Field of the Invention
The present invention relates to a device for distributing and combining microwave electric power between a single waveguide and a plurality of microwave transmission paths.
(2) Description of the Prior Art
In recent years, attempts have been made to use semiconductor amplifier elements such as gallium-arsenic (GaAs) field effect transistors (FET's) instead of conventional traveling-wave tubes, in order to amplify signals in the microwave band. The semiconductor amplifier element, however, has an output power of several watts at the greatest. When it is necessary to amplify a high frequency signal with a great deal of electric power, such elements must be operated in parallel. For this reason, it is accepted practice to distribute input signals in the microwave band into a plurality of channels using a microwave distributor, to amplify the signals of each channel by the above-mentioned semiconductor amplifier element, and to combine the amplified output signals of each of the channels into a signal of one channel using a microwave combiner, thereby obtaining a high frequency at high power. The power, however, is lost when phases of the microwave signal distributed by the microwave distributor are not in agreement, or when the microwave signals are not combined in phase by the microwave combiner. It is, therefore, desired that phases of microwave signals be uniformly distributed in the microwave distributor and in the microwave combiner. It is also necessary that the distributor and the combiner itself lose as little electric power as possible.
FIG. 1A shows a conventional microwave power amplifier, in which a high-frequency input signal IN is divided into four signals using three 3-dB hybrid circuits, the divided input signals are individually amplified by four solid state amplifier elements 2 to 5, and the amplified output signals are combined by hybrid circuits 6, thereby obtaining an amplified high-frequency output signal OUT. In the amplifier of FIG. 1A, when the microwave electric power is distributed from a single waveguide (WG) to a plurality of transmission paths or is combined in the opposite direction, branching points which branch at a ratio of 1:2 or combining points must be provided at each of the places as denoted by reference numeral 1 in FIG. 1B. The distribution of electric power from a single waveguide 7 directly into many transmission paths (such as waveguides) 8-1, 8-2, - - - , or vice versa, is not possible. In the conventional amplifier of FIG. 1A, each of the hybrid circuits 1 or 6 consists of a magic T as shown in FIG. 1C. Therefore, if the magic T's are used at a plurality of branching points, the whole amplifier becomes very bulky and complex in construction. Further, the amplifier element and the waveguide are usually connected via a structure which consists of a connection of a waveguide--a ridge waveguide--an amplifier element with strip lines that serve as input and output terminals--a ridge waveguide--a waveguide. Therefore, the construction is complicated and, moreover, the reliability is not good since the strip lines are connected to the ridge waveguides simply in a pressed manner.